In Wilmington, with roads leading in and out of the city underwater and streams still swelling upward, residents waited for hours outside stores and restaurants for basic necessities like water.

Police guarded the door of one store, and only 10 people were allowed inside at a time.

Woody White, chairman of the board of commissioners of New Hanover County, said officials were planning for food and water to be flown into the coastal city of nearly 120,000 people.

“Our roads are flooded,” he said. “There is no access to Wilmington.”

About 70 miles away from the coast, residents near the Lumber River stepped from their homes directly into boats floating in their front yards; river forecasts showed the scene could be repeated in towns as far as 250 miles inland as waters rise for days.

Downgraded to a tropical depression overnight, Florence was still massive.

Radar showed parts of the sprawling storm over six states, with North and South Carolina in the bull’s-eye.

Tens of thousands were ordered to evacuate from what officials said could be the worst flooding in North Carolina history, but it was not clear how many had fled or even could.

The head of Federal Emergency Management Agency, Brock Long, said officials were focused on finding people and rescuing them.

“We’ll get through this. It’ll be ugly, but we’ll get through it,” Mr Long told NBC’s Meet The Press.

President Donald Trump said federal emergency workers, first responders and law enforcement officials are “working really hard” on Florence.

He tweeted that as the storm “begins to finally recede, they will kick into an even higher gear. Very Professional!”

Tropical Depression Florence moving west (NOAA/AP)

The storm’s death toll climbed to 15 when a pickup vehicle ran off Interstate 20 in South Carolina and struck an overpass support, killing the driver.

Earlier, authorities said a man drowned after his pickup vehicle flipped into a drainage ditch along a flooded South Carolina road and two people died from inhaling carbon monoxide from a generator in their home.

About 740,000 homes and businesses remained without power in the Carolinas, and utilities said some could be out for weeks.

Members of the North Carolina Task Force urban search and rescue team (David Goldman/AP)

Victor Merlos was overjoyed to find a store open for business in Wilmington since he had about 20 relatives staying at his apartment, which still had power.

He spent more than 500 dokkars on cereal, eggs, soft drinks and other necessities, plus beer.

“I have everything I need for my whole family,” said Mr Merlos.

Nearby, a Waffle House restaurant limited breakfast customers to one biscuit and one drink, all take-out, with the price of two dollars per item.

Florence was still spinning slowly above the Carolinas as it pulled warm water from the ocean and hurled it onshore.

Theresa May will be met with a 132-square-metre reminder she supported Remain on her visit to Brussels on Wednesday evening after a British activist group paid for a huge advertisement in the city centre.